Subject: INSERT INTO...RETURNING vs SELECT
From: Cliff Wells <cliff@develix.com>
To: pgsql-sql@postgresql.org
Content-Type: text/plain
Date: Sun, 04 Apr 2010 21:48:52 -0700
Message-Id: <1270442932.4749.140.camel@portable-evil>
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit

I was doing some experimenting and was wondering why the following does
not work:

CREATE TABLE accounts (
  id SERIAL PRIMARY KEY NOT NULL,
  accounts_id INTEGER REFERENCES accounts,
  name TEXT
);

INSERT INTO accounts (accounts_id, name) VALUES (
  (INSERT INTO accounts (accounts_id, name) VALUES (NULL, 'test 1') RETURNING id), 'test 2');

ERROR:  syntax error at or near "INTO"

Of course, the following works fine:

INSERT INTO accounts (accounts_id, name) VALUES (NULL, 'test 1');
INSERT INTO accounts (accounts_id, name) VALUES (
  (SELECT id FROM accounts WHERE name='test 1'), 'test 2');


As far as I can see, INSERT INTO...RETURNING is semantically equivalent
to SELECT...FROM with a side-effect, so it seems this construct should
work.  Can someone shed some light?

Regards,
Cliff